<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <button id="btn" type="button">测试event事件</button>
</head>
<body>
<script>
    onload = () => {
        document.querySelector('#btn').onclick=ev=> {
            console.log(ev.type);
            console.log(ev.target);
            console.log(ev.currentTarget);

        }
        document.onmouseover=function (evt){
            console.log(evt.pageX);
        }

    }
</script>
</body>
</html>